Crystal Engineering through Halogen Bonding:  Complexes of Nitrogen Heterocycles with Organic Iodides

Walsh, Rosa D. Bailey; Padgett, Clifford W.; Metrangolo, Pierangelo; Resnati, Giuseppe; Hanks, Timothy W.; Pennington, William T.

doi:10.1021/cg005540m

Cited by 340 publications

(278 citation statements)

References 38 publications

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“…In addition, this halogen-bonds facilitates the formation of a total of eight hydrogen-bonds in the urea α-tape with a total energy of -76.3 kJ mol Attempts were also made to form gels or co-crystals between 1 and weaker halogenbond donors, namely 1,4-dibromotetrafluorobenzene and 1,4-diiodobenzene. 56 However, no gelation or co-crystal formation was observed in any case confirming the requirement of halogen-bonding strong enough to compete with urea···pyridyl hydrogen-bonding in polar media. …”

Section: Generality Of the Halogen-bond Induced Gelation Mechanismmentioning

confidence: 73%

Halogen-bonding-triggered supramolecular gel formation

et al. 2012

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The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Tunable gel phase materials with novel properties such as switchable rheology and controlled flow characteristics are an emerging topic of interest in potential applications as diverse as pharmaceutical crystallization, catalysis, drug delivery and controlled release, wound healing, and stabilization of drilling mud [1][2][3][4][5][6][7][8][9] . Within this context supramolecular low molecular weight gelators (LMWG), with their reversible and dynamic intermolecular interactions are achieving increasing prominence [10][11][12][13][14][15] . Work on switchable gels includes 2 systems involving photo-, pH, and redox based switching, ultrasound induced gelation, and switchable catalysis [16][17][18][19][20][21][22][23] . In order to systematically develop smart materials with controllable and well understood changes in bulk properties, an understanding of the intermolecular interactions in the system and the way in which they engage in hierarchical self-assembly in order to produce emergent morphologies with complex behavior is required. The link between even primary supramolecular interactions and bulk material properties is often unclear, however. Recent work has highlighted some simple approaches to controllable or smart materials that have met with considerable success. A key theme in particular is setting up a 'tipping point' in a system comprising competing intermolecular interactions which contribute to either gel assembly or gel dissolution. In this way a number of research groups have shown that anion binding in competition with urea self-assembly can be used to 'turn-down' and ultimately 'turn-off' gelation behavior 24,25 . Interestingly, in alternative systems, anion binding has also been used to induce gelation 26,27 . In a similar way metal coordination has also been used to tune gel properties 25 . In a series of bis(urea) gels we have shown how a combination of metal-and anion-binding can allow comprehensive control over the system. Competitive anion binding reduces gel strength by inhibiting urea -tape hydrogen-bond formation [28][29][30][31] .Conversely, metal coordination in pyridyl-urea compounds results in metal binding to the pyridyl group which suppresses the alternative, gel-inhibiting urea-pyridyl hydrogenbonding interaction, freeing the urea groups to form fibrils, and hence gels, as a result of the urea tape hydrogen-bonding motif [32][33][34] . These competitive interaction modes are summarised in Figure 1. 3

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Section: Generality Of the Halogen-bond Induced Gelation Mechanismmentioning

confidence: 73%

Halogen-bonding-triggered supramolecular gel formation

et al. 2012

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“…This is supported by the similarity of structural motifs found in co-A C H T U N G T R E N N U N G crystals involving either tfib or 1,4-dibromotetrafluorobenzene (tfbb). [17,20] As a means of exploring the anticipated isostructurality, we attempted the synthesis of tfib cocrystals with all HN-, O-, and S-congeners of tox and tmo: morpholine, piperazine, dioxane and dithiane. We also proceeded to construct corresponding cocrystals using tfbb (Scheme 2).…”

Section: Resultsmentioning

confidence: 99%

“…· cocrystals · functional materials · halogen bonds · supramolecular chemistry atoms heavier than oxygen, we decided to construct cocrystals using tetrafluoro-1,4-diiodobenzene (tfib) as a halogenbond donor [17] and readily available sulfur-containing molecules 1,4-thioxane (tox) and 1,4-thiomorpholine (tmo) as the acceptors (Scheme 1 a). [18] We anticipated that cocrystallization of tfib with either tox or tmo would result in the formation of one-dimensional polymer chains of alternating donor and acceptor molecules, held together by halogen bonds (Scheme 1 b).…”

Section: Abstract: a C H T U N G T R E N N U N G Mechanochemistrymentioning

confidence: 99%

Isostructural Materials Achieved by Using Structurally Equivalent Donors and Acceptors in Halogen‐Bonded Cocrystals

Cinčić

Friščić

Jones

2007

Chemistry A European J

239

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We demonstrate the supramolecular and structural equivalence of two halogen-bond donors (I and Br) and three acceptors (O, NH and S) through the synthesis of seven isostructural halogen-bonded cocrystals, involving six different molecules: 1,4-dibromo- and 1,4-diiodotetrafluorobenzene (donors) and thiomorpholine, thioxane, morpholine, and piperazine (acceptors). The formation of isostructural cocrystals indicates how cocrystallization may be used to overcome shape and functional group dissimilarities that control molecular arrangement in the solid state. The differences in composition between the seven isostructural cocrystals directly affect the strength and nature of halogen bonds between their constituents, allowing the systematic variation of cocrystal physical properties, in particular the melting point, without affecting their crystal structure. Replacement of each O or S halogen-bond acceptor with an NH group provided an approximate 70 degrees C increase in melting point, whereas the replacement of I with Br as the halogen-bond donor lowered the melting point of the resulting solid by a similar amount.

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“…[538] Besonders die leicht polarisierbaren Iodgruppen zeigen jedoch häufig Kontakte unterhalb der Summe von Van-der-Waals-Radien. [539] Die Einführung von Bromsubstituenten in Chinolinium-Gastverbindungen erhöht die Affinität zu Cyclophan-Gastmolekülen in wässrigem Medium um etwa 1 kJ mol À1 . [540] Die bereits diskutierten dispersiven Wechselwirkungen von Sauerstoff-und besonders Schwefelgruppen lassen sich durch Messungen der Rotamerengleichgewichte von Triptycenderivaten skalieren, in denen ein Kontakt zwischen den Alkoxyketten und den an der 9-Position substituierten Phenylgruppen möglich ist (Schema S24).…”

Section: Angewandte Chemieunclassified

Bindungsmechanismen in supramolekularen Komplexen

Schneider

2009

Angewandte Chemie

185

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Kräfte‐Sammelsurium: Supramolekulare Komplexe, wie der gezeigte, beruhen meist auf einer Kombination unterschiedlichster Wechselwirkungen, wie Ionenpaarbildung, Wasserstoffbrücken und Stapelwechselwirkungen. Die nicht immer einfache Charakterisierung von Natur und Stärke der intermolekularen Kräfte liefert Beiträge zum Verständnis biomimetischer Systeme wie auch zum Design von synthetischen Rezeptoren, Wirkstoffen und intelligenten Materialien. Die supramolekulare Chemie hat in den letzten Jahren eine enorme Ausdehnung erfahren, sowohl mit Blick auf mögliche Anwendungen wie auch auf analoge biologische Systeme. Bildung und Funktion supramolekularer Komplexe werden durch eine Vielzahl von oft schwer zu differenzierenden nichtkovalenten Kräften bestimmt. Ziel dieses Aufsatzes ist es, die entscheidenden Wechselwirkungsmechanismen zusammenhängend darzustellen und das Gesamtgebiet auf diese Weise zu klassifizieren. Als Beispiele werden meist organische Wirt‐Gast‐Komplexe gewählt, unter Berücksichtigung auch von biologisch relevanten Fragestellungen. Das Verständnis und die Quantifizierung der intermolekularen Wechselwirkungen ist für die rationale Planung neuer supramolekularer Systeme, einschließlich intelligenter Materialien, ebenso von Bedeutung wie für die Entwicklung neuer Wirkstoffe.

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Crystal Engineering through Halogen Bonding: Complexes of Nitrogen Heterocycles with Organic Iodides

Cited by 340 publications

References 38 publications

Halogen-bonding-triggered supramolecular gel formation

Halogen-bonding-triggered supramolecular gel formation

Isostructural Materials Achieved by Using Structurally Equivalent Donors and Acceptors in Halogen‐Bonded Cocrystals

Bindungsmechanismen in supramolekularen Komplexen

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